1. Field of the Invention
This invention relates to an improved process for obtaining durable press fabrics which exhibit no discoloration and which have higher strength than normally encountered in fabrics treated for durable press properties with a crosslinking agent and an aluminum salt catalyst. Specifically, this invention relates to use of the aluminum acetate salt-sodium chloride mixture produced from reaction of aluminum chloride and sodium acetate as catalyst in formulations containing formaldehyde or a formaldehyde-amide adduct crosslinking agent. Fabrics treated with said formulations have durable press properties and benefit by having no discoloration but higher strength than similarly treated fabrics in the singular presence of either aluminum chloride or sodium acetate as catalyst.
2. The Prior Art
Reeves et al., U.S. Pat. No. 3,526,474, employed metal acetates as polymerization catalysts in a novel finishing treatment for cotton. Although use of aluminum acetate was not demonstrated, Reeves et al., teach that this metal acetate, as well as magnesium acetate and zirconium acetate, is an effective polymerization catalyst. A requirement for polymerization catalysts to be suitable is that they be salts of a weak acid and a weak base. Such catalysts predominantly promote homopolymerization, or copolymerization when a mixture of aminoformaldehyde condensation products are present, to produce insoluble products within a cellulosic fiber rather than promote reaction of the agent with the cellulose. Evidently, the cellulose molecules are not crosslinked appreciably as they do not exhibit significant improvements in conditioned wrinkle recovery angles even though agents which are capable of crosslinking cellulose were cured in the fabrics at elevated temperatures.
Bacon, U.S. Pat. No. 2,992,138, used sodium acetate with zinc nitrate as a catalyst system for treatments with dimethylol ethyleneurea to reduce fabric yellowing, reduce strength loss, and reduce adverse effect on the shade of dyes as caused by zinc nitrate when it alone was used as catalyst.
Irvine and coworkers, American Dyestuff Reporter 48 (12), 37-42, 50 (1959), used modifying salts such as aluminum formate or magnesium chloride with aluminum chloride to avoid two serious disadvantages of aluminum chloride by itself. These disadvantages are: its permanent and high acidity results in excessive tendering of cellulosic fabrics; and its high acidity catalyzes resin condensation in treatment baths causing precipitation.
Hood and Ihde, Journal American Chemical Society, 72, 2094 (1950), by double decomposition of sodium acetate and aluminum chloride prepared basic aluminum acetate which was insoluble in water. These same workers, supra, also produced aluminum triacetate in the absence of water to prevent hydrolysis to Bohmite, AlO(OH).
The aluminum salts, Al(NO.sub.3).sub.3, Al.sub.2 (SO.sub.4).sub.3, and AlCl.sub.3 are very strong catalysts but each has inherent disadvantages which seriously limit their utility in textile finishing. In addition to those disadvantages cited above for AlCl.sub.3, Al(NO.sub.3).sub.3 tenders fabric very badly and causes yellowing which is attributable to oxidation, while Al.sub.2 (SO.sub.4).sub.3 also causes tendering and yellowing at curing temperatures of 140.degree. C. and higher.
In the prior art, no suitable means is disclosed for employing an aluminum acetate salt as catalyst in treatments with a cellulose crosslinking agent to produce a satisfactory level of durable press properties in finished fabrics. Homopolymerization or copolymerization of crosslinking agents result on use of aluminum acetate or magnesium acetate rather than effective crosslinking of the cellulose that is needed for the improved wrinkle recovery necessary for durable press performance. The aluminum salts, AlCl.sub.3, Al.sub.2 (SO.sub.4).sub.3, and Al(NO.sub.3).sub.3, although strong catalysts for the crosslinking of cellulose with methylolamide agents, produce undesirable tendering of the fabric and discoloration.